Amide-modified compounds as such are known. For instance, amides of pyridylalkylamines are known from U.S. Pat. No. 4,794,121 as products with pharmacological activity, among which are analgesic, antispasmodic, bronchodilator, antianoxic, and anticonvulsant activity. In Japanese patent application JP 50120485 piperazinylethyl lauramide is disclosed as an antistatic agent for PVC. Similar compounds were disclosed in EP 402,266 to exhibit antiseptic, antimicrobal, and disinfectant activity. Aminoalkylene amides with piperazinyl groups are disclosed in U.S. Pat. No. 3,284,177 as deposit-reducing additives to gasoline, and similar compounds are known from JP 10212275 to behave as lubricating substances for magnetic recording mediums.
In accordance with the invention, amide-modified compounds are used in a method for dispersing a pigment. This method can be used, for example, for producing a pigment concentrate and/or a coating composition. Popular pigment dispersing processes include flush and dry grind.
Pigments are generally produced in an aqueous medium. One of the steps in the manufacture of pigments is the precipitation from water. After precipitation of the pigment, the pigment/water mixture is filtered to provide a filter cake or presscake containing pigment and residual moisture.
When the pigment is to be incorporated in an organic or non-aqueous system for application to a substrate, it is necessary to remove the residual moisture from the filter cake or presscake. The presscake typically contains 30 to 80% by weight of water. Removal of residual water from a presscake is usually accomplished by a process of water displacement that is known as “flushing.”
Flush processes are dispersion processes, such as those described in Kirk-Othmer, Encyclopedia of Chemical Technology, Ed. M. Grayson et al., John Wiley & Sons (3rd Ed. Vol. 17) 1982, pp. Cover, Contents 838-864, 871-873; and The Printing Ink Manual, Society of British Printing Ink Manufacturers LTD, Leach, D. H., et al. (5th Ed.), pp. Cover Contents, 709-710, 373, 814.
Generally speaking, flushing is the direct transfer of pigments in an aqueous phase to an oil or non-aqueous phase without intermediate drying. Flushing of the pigment is carried out by intensely mixing the presscake with a flushing varnish and/or ink solvent. A “flushing varnish” is an ink solvent containing a resin dissolved therein. The solvent and/or flushing varnish is often referred to as a “flushing agent.” The term “ink solvent,” as used herein, refers to any petroleum or vegetable derived material, which may be used to hold the resin system in solution.
As the pigment is wetted by the flushing agent, the water is driven out of the presscake until only a small percentage of water remains. The last traces of water are removed by applying a sub-atmospheric pressure and/or heat to the presscake. The flushing agent in effect flushes the water from the pigment resulting in pigment dispersion in the base of a coating/ink composition. Alkyd resins are sometimes used in addition to and as the flushing agent to assist in the break-out of water from the presscake.
Pigments at the presscake stage of manufacture have a particle size that is more suitable for generating maximum gloss and color strength in formulations than pigments in their finished dry form. Accordingly, flushed pigments produced without first drying the pigment are e.g. preferred colorants for lithographic ink formulations.
Problems may occur if the flush resin is too polar and the water layer will not be separated. If the flush resin is too apolar, the pigment particles will not properly be dispersed. These problems have now been solved by using the amide-modified resin or hydrocarbyl moiety in accordance with the invention.
The amide-modified resin or hydrocarbyl moiety is also advantageously used in other dispersing processes in accordance with the invention. Another exemplary dispersing process is dry grind. Grinding reduces particle size by mechanical means. It is an example of milling which can be used to obtain paint and other pigmented products. Generally, milling or grinding proceeds first by wetting pigment particles. Usually a dispersant, such as that utilized in the claimed invention, is added at this stage. The dispersant or dispersing agent can be added alone or in combination with other materials, such as a varnish. After wetting the pigment particles, the milling/grinding process usually breaks down larger particles under shear forces and then disperses the resulting smaller particles within the medium.